Method for synchronzing audio and video data in avi file

Abstract

A method for synchronizing audio and video data in an Audio Video Interleave (AVI) file, the AVI file containing a plurality of audio and video chunks, includes: determining a frame rate error of a group of consecutive main access units (GMAU) according to a video clock and an audio clock; determining a GMAU presentation time stamp (PTS) according to the frame rate error; and updating the AVI file with the GMAU PTS, so the GMAU will be played utilizing the GMAU PTS.

1 . A method for synchronizing audio and video data in an Audio Video Interleave (AVI) file, the AVI file comprising a plurality of audio and video chunks where the AVI file is grouped into one or more Group Main Access Units (GMAUs), the method comprising:
 determining a frame rate error of a GMAU according to a video clock and an audio clock;   determining a GMAU presentation time stamp (PTS) according to the frame rate error; and   updating the GMAU with the GMAU PTS, so the GMAU will be played utilizing the GMAU PTS.   
   
   
       2 . The method of  claim 1 , further comprising:
 multiplexing the audio and video data of the GMAU.   
   
   
       3 . The method of  claim 1 , wherein the video clock is derived from video-sync of the video frames and the audio clock is derived from a system time clock (STC). 
   
   
       4 . The method of  claim 1 , wherein the length of a GMAU is defined by considering a clock rate difference between the audio clock and video clock. 
   
   
       5 . The method of  claim 1 , wherein the GMAU presentation time stamp is recorded in a private chunk of the AVI file. 
   
   
       6 . A method for synchronizing audio and video data in an Audio Video Interleave (AVI) file, the AVI file comprising a plurality of audio and video chunks, the method comprising:
 determining a frame rate error according to a video clock and an audio clock;   comparing the frame rate error with a frame duration; and   selectively adding or dropping at least a video frame according to the comparison result.   
   
   
       7 . The method of  claim 6 , further comprising:
 multiplexing the audio and video data;   wherein the step of comparing the frame rate error with a frame duration comprises:   when the frame rate error is equal to or greater than the frame duration, determining a number of video frames to be added or dropped, and when the frame rate error is less than the frame duration, accumulating the frame rate error to the subsequent GMAU.   
   
   
       8 . The method of  claim 6 , wherein the step of selectively adding at least a video frame comprises repeating at least one video frame. 
   
   
       9 . The method of  claim 6 , wherein the video clock is derived from video-sync of the video frames and the audio clock is derived from a system time clock (STC). 
   
   
       10 . A method for synchronizing audio and video data in an Audio Video Interleave (AVI) file, the AVI file comprising a plurality of audio and video chunks, the method comprising:
 determining a frame rate error according to a video clock and an audio clock;   comparing the frame rate error with a frame duration; and   selectively adding or dropping at least an audio frame according to the comparison result.   
   
   
       11 . The method of  claim 10 , further comprising:
 multiplexing the audio and video data;   wherein the step of comparing the frame rate error with a frame duration comprises:   when the frame rate error is equal to or greater than the frame duration, determining a number of audio frames to be added or dropped, and when the frame rate error is less than the frame duration, accumulating the frame rate error to the subsequent GMAU.   
   
   
       12 . The method of  claim 10 , wherein the step of selectively adding at least an audio frame comprises repeating at least one audio frame. 
   
   
       13 . The method of  claim 10 , wherein the video clock is derived from video-sync of the video frames and the audio clock is derived from a system time clock (STC).